Introduction to Midterm Exams

            You are responsible for lecture material and reading assignments, but the exam will emphasize material covered in lecture.  The exam will be worth 100 points.  You need bring only a pen (bring 2), since we will not use Scantron or Zeus forms.  But you must use a pen, not a pencil.  We will hand out the exams at 9:10 sharp, so be in your seat and ready to go at that time. There should be enough space to sit at least every other seat, so please space yourselves accordingly. The exam ends at 10:00 sharp — if we do not have your exam at that time, it will not be graded.

            We will have several types of questions on the exam, and provide examples of some of the most likely formats below.  These questions do not constitute a study guide; they are just indications of the types of questions that might be posed.  Please consider organizing your thoughts carefully in such a way as to be able to answer thoroughly and concisely questions like any of those posed below. We urge you to design your course of study accordingly.  Following the example questions are some thought questions to help you prepare for the exams ahead of you in Biology 240.

Sample Question Styles

I. Temporal Sequences

Place the following events in their proper order, starting with 1 for the earliest, 2 for the next earliest, etc.  Hint:  Think about the organisms in which these features first occurred.  It almost helps to think of how these events could by overlaid on an evolutionary tree of life.  For example, in this question, think about which features occur only in eukaryotes, and which occur in prokaryotes.  Those occurring in prokaryotes would have come first.  Questions of this form may also appear in the short-answer section (and an example is given below).

            _____  Cells undergo meiosis for the first time.

            _____  Cells undergo glycolysis for the first time.

            _____  Cells respire with oxygen for the first time.

            _____  Cells undergo mitosis for the first time

II.  Matching.  Match the taxonomic groups on the right with the appropriate terms on the left.  There is only one correct answer for each group.

_____            1.  Fungi                                  a.  sister group of animals

_____            2.  Cyanobacteria                     b.  contains chloroplasts

_____            3.  Brown algae                        c.  photosynthetic prokaryote

                                                                     d.  normally locomotes by undulipodia

III.  True/False.  Write T or F in the space next to each statement.

_____            1.  Bacterial cells undergo sexual reproduction, alternating meiosis and syngamy.

_____            2.  Natural selection anticipates changes in the environment.

_____            3.  The nucleus of eukaryotes probably arose endosymbiotically.

_____            4.  Life is not possible without free oxygen.

IV.  Multiple Choice.  Place the letter of the best answer in the space provided.

____ 1.  Gene flow:  a) operates only in small populations,  b) operates only in large populations,  c) may cause changes in allele frequencies in a population,  d) affects mutation rates,  e) helps to maintain the Hardy-Weinberg equilibrium.

____ 2.  Directional selection acts to:  a) change the phenotype of the individual,  b) change the genotype of the individual,  c) change allele frequencies in a population,  d) create new alleles,  e) preserves genetic diversity.

____ 3.  Which of the following is a mechanism that has been proposed to explain the abiotic formation of organic polymers from organic monomers in the origin of life?  a) adherence to the charged surface of minerals;  b) formation of organic “bubbles;”  c) photosynthesis;  d) the Genetic Code;  e) endosymbiosis.

____ 4.  Different groups of photosynthetic eukaryotes possess different photosynthetic pigments.  According to serial endosymbiotic theory, these differences are due to:  a) divergent evolution among eukaryotes,  b) genetic drift,  c) acquisition of different photosynthetic prokaryotes by eukaryotes,  d) special creation.

____5. Gram negative bacteria: (a)   have a thick peptidoglycan layer (b)  stain purple (c)   have a cell wall that lacks an outer membrane (d)  have a lipopolysaccharide outer layer

____6. The bacterial endospore: (a)   lacks DNA (b)  contains a water supply (c)   occurs when resources are scarce (d)  all of the above

____7. A photoheterotroph uses light as a source of: (a) carbon (b) energy (c) water (d) protein

____8. Which of the following was not in the early atmosphere? (a)   water (b)  nitrogen (c)   methane d) oxygen gas

V.  Fill in the Blank.  Fill in each blank with the appropriate word or short phrase, or circle the correct term.

1.  The Class Reptilia includes lizards, turtles, crocodiles, dinosaurs, etc., but not the birds, which we think descended from a group of dinosaurs.  Thus the Reptilia would be considered _________-phyletic.

2.  ___________________ speciation involves separation of large portions of an ancestral population.

3.  Phylogenetic classification uses shared __________________ characters, rather than overall similarity, to classify organisms.

4.  The most recent “universal ancestor” of the Domain Archaea, Domain Eukarya, and Domain _______________ probably metabolized aerobically / anaerobically / hydrophobically (circle one) and utilized RNA / DNA / proteins / starches / fatty acids (circle one) as its genetic material. 

VI.  Short Answer.  Answer each question in a short essay, or list if appropriate.

1.  Place the following three events in the order that they most likely occurred (from earliest to latest), AND explain the reasons you placed them in that order. 

(c) origin of DNA as the genetic material

 (b) origin of aerobic respiration 

 (c) origin of mitosis

2.  Describe why we think that mitochondria were originally endosymbiotes.

3.  Describe why shared derived characters  (and not shared ancestral characters) are the definitive criteria for defining monophyletic groups.

4.  Neutral models (like the Hardy-Weinberg equilibrium) are useful in biology (and other sciences).  But why are they useful, if such models do not accurately describe the “real world”?